著者

TAKAMURA Tamio IRIE Hitoshi

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2019-059, (Released:2019-08-09)

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The accurate aerosol optical thickness is indispensable for estimating the radiative forcing of aerosols in the atmosphere. Sun photometry is one of the most popular methods, which is simple and easy to use, but it should be noted that some errors due to forward scattering effect can be introduced in the observation of the direct normal irradiance. Consequently, the estimated optical thickness of aerosols can be under-estimated even if the calibration constant is correct. This possibility depends on an optical geometry of the measuring instrument as well as aerosol characteristics. This report assesses these effects by assuming several aerosol types and instrumental parameters quantitatively. Forward scattering ratio γλfwd, which is defined as a ratio of the forward scattering part to the true direct normal irradiance (Iλ), by Iλobs=Iλ(1+γλfwd), is approximately proportional to the product of the optical thickness (τλaer) and the single scattering albedo (ωλ) of aerosols and the relative air mass (m), γλfwd≈ελωλτλaerm. The coefficient ελ is a proportional constant which is dependent on the opening angle of the instrument as well as the optical characteristics of aerosols. The variation of ελ is tabulated for several aerosol types and opening angles. Then the error for the estimate of τλaer can be approximately expressed by Δτλ≈ -ελωλτλaer.

著者

KAJINO Mizuo DEUSHI Makoto SEKIYAMA Tsuyoshi Thomas OSHIMA Naga YUMIMOTO Keiya TANAKA Taichu Yasumichi CHING Joseph HASHIMOTO Akihiro YAMAMOTO Tetsuya IKEGAMI Masaaki KAMADA Akane MIYASHITA Makoto INOMATA Yayoi SHIMA Shin-ichiro TAKAMI Akinori SHIMIZU Atsushi HATAKEYAMA Shiro SADANAGA Yasuhiro IRIE Hitoshi ADACHI Kouji ZAIZEN Yuji IGARASHI Yasuhito UEDA Hiromasa MAKI Takashi MIKAMI Masao

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2019-020, (Released:2018-12-09)

被引用文献数

36

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Model performance of a regional-scale meteorology – chemistry model (NHM-Chem) has been evaluated for the consistent predictions of the chemical, physical, and optical properties of aerosols. These properties are essentially important for the accurate assessment of air quality and health hazards, contamination of land and ocean ecosystems, and regional climate changes due to aerosol-cloud-radiation interaction processes. Currently, three optional methods are available: the 5-category non-equilibrium, 3-category non-equilibrium, and bulk equilibrium methods. These three methods are suitable for the predictions of regional climate, air quality, and operational forecasts, respectively. In this paper, the simulated aerosol chemical, physical, and optical properties and their consistency were evaluated by using various observation data in East Asia. The simulated mass, size, and deposition of SO42- and NH4+ agreed well with the observations, whereas those of NO3-, sea-salt, and dust needed improvement. The simulated surface mass concentration (PM10 and PM2.5) and spherical extinction coefficient agreed well with the observations. The simulated aerosol optical thickness and dust extinction coefficient were significantly underestimated.

著者

KHATRI Pradeep HAYASAKA Tadahiro IWABUCHI Hironobu TAKAMURA Tamio IRIE Hitoshi NAKAJIMA Takashi Y.

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2018-036, (Released:2018-04-09)

被引用文献数

9

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The present study implements long-term surface observed radiation data (pyranometer observed global flux and sky radiometer observed spectral zenith transmittance data) of multiple SKYNET sites to validate water cloud optical properties (cloud optical depth COD and effective radius Re) observed from space by MODIS onboard TERRA and AQUA satellites and AHI onboard Himawari-8 satellite. Despite some degrees of differences in COD and Re between MODIS and AHI, they both showed common features when validated using surface based global flux data as well as cloud properties retrieved from sky radiometer observed zenith transmittance data. In general, CODs from both satellite sensors are found to overestimated when clouds are optically thin. Among a number of factors (spatial and temporal variations of cloud, sensor and solar zenith angles), the solar zenith angle (SZA) is found to have an impact on COD difference between reflectance based satellite sensor and transmittance based sky radiometer. The Re values from the sky radiometer and satellite sensor are generally poorly correlated. The difference in Re between the sky radiometer and satellite sensor is negatively correlated with COD difference between them, which is likely due to the inherent influence of Re retrieval precision on COD retrieval and vice versa in transmittance based sky radiometer.